Phagocytes, which play a central role in host defense are modulated by external regulatory molecules known as macrophage activating factors such as gamma-interferon (9-IFN). Gammainterferon interacts with a specific cell surface receptor on Phagocytes which results in either the activation or the repression of specific genes, the net effect being macrophage activation. A number of g-IFN responsive genes have been characterized in macrophages, some of which are restricted to myeloid monocytic lineage. The goal of this proposal is to identify new genes which are 9-IFN responsive and myeloid monocytic specific as it is likely that these novel proteins may play a key role either directly in host defense or in regulation of macrophage function. Specifically, my goal is to identify g-IFN inducible RNA transcripts by several techniques which make use of differential screening, subtractive libraries and subtractive hybridization probes. The primary sequence of the inducible proteins will be used as a guide to develop the initial strategy for their identification and characterization. Radiolabelled cDNAs will be used to identify their respective gene(s) with a view to identifying cis-acting regulatory elements. In particular, putative Promoter/enhancer elements which may confer lineage specificity and 9-IFN responsiveness will be identified by expression experiments in which varying lengths of the 5'flanking region are introduced into phagocytic and non-phagocytic cell lines. The ability to introduce cloned genes into cell lines will also allow us to investigate the functional properties of the protein(s). Although it is apparent in phagocytic cells that at least several genes are responsive to g-IFN, an understanding of their molecular expression will provide insights into coordinated mechanisms of host defense in both normal and pathological states.